The present invention relates to novel organic amide compounds, procedures for preparing the compounds, pharmaceutical compositions containing the same and methods for using the compounds. These novel organic amides are primarily comprised of a carboxylic acid moiety and a nitrogenous lipid moiety.
Numerous compounds are known to be active in vitro and yet exhibit little or no activity in vivo. In particular, numerous carboxylic acids are known to be important in the actions of the peripheral and central nervous systems and are active in vitro but are either non-active or only slightly active in vivo. Gamma-aminobutyric acid (GABA), for example, is known to be active on the central nervous system in vitro and has been suggested as a possible inhibitory transmittor (Louis S. Goodman and Alfred Gilman, The Pharmacological Basis of Therapeutics, 4th Ed., p. 429 (1970)). However, GABA has been found to be ineffective when administered in vivo as measured by convulsion tests in mice.
The present inventors have found that compounds of the formula I, prepared by combining a carboxylic acid, such as GABA, with a nitrogenous lipid, such as a phospholipid or sphingosine, provide amide compounds which are active in vivo, exhibiting activities far superior to that of the corresponding carboxylic acid or lipid compounds administered alone. For example, the amide of GABA with a sphingosine provides a compound which is far more active in vivo than is GABA alone. Similarly, lysergic acid, dihydrolysergic acid and isolysergic acid are essentially inactive when administered alone, but when combined with a sphingosine provide compounds of the formula I which have significant in vivo activity as measured by hypoprolactinemic effects in rats.
The significantly improved pharmacological properties of the compounds of formula I are thought to result from the ability of these compounds to penetrate the hematoencephalic barrier and/or reach the peripheral organs far better than the carboxylic acid compounds alone. This ability of the compounds of the present invention favors the interaction between the biologically active compound, such as the carboxylic acid, and the situs of the specific interactions present in the membranes.
Hence, the compounds of the present invention are useful for enhancing or increasing the in vivo biological activity of in vitro biologically active carboxylic acids as well as stimulating the in vivo biological activity of in vitro biologically active carboxylic acids which have little or no in vivo activity.